Apparatus for lapping or abrading



' Aug. 22, 1939. w. E. HC\ KE 2,170,329

APPARATUS FOR LAPPING OR ABRADING Filed Nov. 10, 1937 2 Sheets-Sheet 13nventor WILLIAM E. HDKE attorney Aug. 22; 1939. w. E. HOKE 2,170,329

APPARATUS FOR LAPRING 0R ABRADING Filed Nov. 10, 1937 2 Sheets-Sheet 2WIL LIA M .E. HDKE Patented A... 22, 1939,

' UNITED STATES PATENT OFFICE A I APPA'R/ATUS FOR L ZLZZTG 0R ABRADINGWilliam E. Holre, Baltimore, Md. Application November 10, 1937, SerialNo. 173,888

. 4 Claims.

The invention relates to lapping or abrading. This application is a.continuation in part of copending application Serial No. 155,845 filedJuly 27,1937. In another application filed of evendate herewith I claimthe art or method herein disclosed.

Qne object of the invention is to provide apparatus for lapping orgrinding in accordance .with which extremely accurate results may be Pachieved. Another object of the invention is to provide apparatus forthe lapping of internal bores to a high polish and extremely accuratelimits. Another object of the invention is to provide apparatus to causethe thermal expan- 15 sion or contraction of a grinding or lappingelelapping fuel pumps and injection nozzles of Dieselment. Anotherobject of the invention is to provide lapping apparatus for lapping thebores of articles in which errors of alignment are obviated by a certainradial freedom of movement of either the lapping tool or the workholding device. 'Another object of the invention is to provide anapparatus having a plurality of lapping stations in a container for afluid into which the lapping ",tool enters, whereby gradually to heatthe tool, performing successive lapping operations on the work pieces invarying sequences. Another ob'-, ject of the invention is to provideapparatus for grinding the bores of a plurality of articles so that theyare all interchangeable with a given piston or set of pistons and varyin diameter only by very minute amounts. Another object of the inventionis to provide apparatus for grinding or engines. Another object of theinvention is to provide an apparatus effective for removing metal inamounts under one ten thousandth of an inch ject of the invention is toprovide an effective apparatus for the lapping of small articles.

Other objects will be in part obvious or in part pointed outhereinafter.

i The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts, as will beexemplified in the structure to be hereinafter described, and the scopeof the application of which will be indicated, in the following claims.

In the accompanying drawings, in which is illustrated one of manypossibleembodiments of apparatus constructed according to the invention,

Figure 1 is a plan view of the apparatus; Figure 2 is an elevation ofthe same with the container wall shown in section;

Figure 3 is a detailed viewof a catch to hold the clamp for the articlein place;

Another ob- Figure 6 illustrates'still another form of lap,

lapping an article having a bore open at each end;

Figure 7 is a sectional view illustrating still another modification inwhich the lap is in two parts;

Figure 8 is a view 'of the top of the lap shown in Figure 7 with thearbor removed;

Figure 9 is a sectional view of still. another modification in which thelap is in two parts, as in the case of the lap of Figure 7, showing,however, a difierent type of connection;

Figure .10 is a side elevation of still another modification of the lap,showing another maner of connecting the lap to the arbor;

Figure 11 is a plan view of the lap shown in Figure with the arborremoved.

Referring first to Figures 1 and 2, I provide a container I havingtherein a liquid for the transfer of heat. Because of the fact that italso acts as a lubricant, kerosene has certain definite advantagesin'this connection, but other liquids may be used depending upon theexact conditions in any particular grinding or lapping operation.

The invention makes use of differences'in the thermal expansion of thearticle to be lapped or ground and the lapping tool or wheel and,therefore, with a given set of coeflicients of expansion, the greaterthe temperature difference the more material can be removed. I may,therefore, in some cases wish to use a liquid which can be successfullyraised to a higher temperature than kerosene, but excellent results inactual practice have been achieved with :erosene, it being a goodlubricant as aforesaid.

In the center of the container l is a standard 2 which supports arotatable plate 3 by means of ball bearings 4. This plate 3 has aplurality of openings 5 arranged symmetrically therein and each opening5 has an index number 6. In the illustrative embodiment of thisinvention there are thirty-six openings numbered from 1 to 36, asclearly shown in Figure 1. In each opening 5 there is placed an articleT to be lapped. The specific articles to be lapped in this-illustrativeembodiment of the invention are injection nozzles for Diesel engines. Asbetter shown in Figure 9,

these nozzles l have one closed or blind end and' one open end with anannular flange 8 which rests upon the plate 3.

Fuel pumps and injection nozzles of small size high speed Diesel enginesmust function with a high degree of accuracy, in view of-the very smallquantities of fuel injected for each working stroke of the engine. Inthe case of an engine running at two, thousand R. P. M., injection mayhave to be completed in about two thousandths of a second and if theengine is of a four cycle type, each fuel pump and injection nozzle mustgo through the injection process one thousand times per minute. If theengine is of the two cycle type, at two thousand R. P. M., injectionmust occur two thousand times per minute for each cylinder. The sizes ofthe fuel pumpand injection nozzle of such an engine areso small that itis not practical to use piston rings or other means to insureaccuratefltting. The plungers and cylinders must be lapped with aclearance not t9 exceed one ten thousandth of an inch and to obtain suchaccuracy has been a very diflicult problem in this art heretofore. Theouter cylindrical members of the. injection nozzle and fuel pump are notonly. hardened but nitrided before being lapped for final use. Thehardening process, if done after the lapping, would so warp the surfacesthat they would lose their accuracy of fit, and cause leakage.

The container I is filled with kerosene or others liquid to above thelevel of the tops of the flanges 8 so that it will reach the lappingtool and heat the lapping tool while lapping takes place. To permit freecirculation of the liquid in order to facilitate the transfer ofheat, Iprovide holes 9 in the plate '3, as clearly shown in Figure 1.

Referring again to Figures 1 and 2, the standard 2 has projecting fromits center a standard III on which is pivotally mounted a hand lever II.The container I has preferably equally distributed around itscircumference three supports I 2 which serve to maintain the plate 3 ina horizontal position. Over one of these supports I2 and hinged to theside of the container I is a clamp I3 which has in its center, whenhorizontal, a vertical .opening I4 substantially the finished size ofthe bore of the article to be lapped. This opening has a slightlyflared-top portion I5 to form a lead for the lap. The lower portion ofthe admits the heated fluid to the opening or bore I4 and also to thebore in the article I. Thereby the heated fluid is brought in contactwith the lapping tool to heat it. The article I has holes la in thebottom thereof which are the discharge openings for fluid in the articlewhen it is used as a Diesel fuel pump and injection nozzle, and theseopenings serve to permit the oil to be discharged downwardly, thusavoiding a hydraulic lock when'the lapping tool enters.

The free endof the clamp I3 is forked and a link I8 is pivotallyfastened to the clamp I3 in this forked portion. The'upper end of thelink I8 is .forked and in the sides of the fork are elongated slots I9receiving a pin 2|] extending through the end of the lever II. A springI8a surrounds the link I8 extending between the forked portion of theclamp I3 and a washer IBb which abuts the end of the lever II. When thelever II is in the position shown in Figure 1, the spring I8a holds theclamp I3 resiliently against the flange 8 of one of the articles I. Bylowerirr= the outer end of the lever I I, thus raising the link I8, theclamp I3 is raised to permit the plate .3 to be-indexed to bring anotherarticle! into position to be clamped in place for lapping. As shown inFigures 1, 2 and 3, the outer end of. the lever II is held in theresilient holding position of Figure 'l by a catch 2| which is pivotedto a standard 22 attached to the container wall. This catch has a handleportion 2Ia by means of which it may readily be released in order tolower the outer end of the lever II and thus raise the clamp I 3.Raising the clamp I3 releases a particular work piece I and allows theoperator to index the plate 3 to bring another work piece into line withthe clamp I3, whereupon he may clamp such work piece in position to belapped. The plate 3, when the clamp I3 is released, is freely rotatableand a stick or the like may be used to index it into a new position.

I provide an electric coil 23 in the bottom of the container I to heatthe liquid to a given amount and to maintain the temperature that isdesired. Preferably I provide baffles or paddle plates 23a on the underside of the plate 3 to agitate the liquid whenever the plate 3 isindexed, thereby to distribute the heat more effectively. The electriccoil 23 may be energized through a thermostatically operated switch 24which is controlled by a thermostat bulb 25 placed in the bottom of thecontainer, preferably near the lapping station. As a guide to theoperator, a thermometer 26 may also be placed in the liquid. I provide adischarge valve 21 for withdrawing the liquid from the container. Theliquid may be discharged from the container when it is desired to starta new series of lapping operations with cool liquid, or anyother desiredmanner of cooling the liquid may be adopted.

Practically any form of drill press may be used having a chuck to holdthe lap and to rotate it and to allow it to be raised and lowered at thewill of the operator. In Figure 2 a chuck 28 is shown containing a lap29 held by its arbor 30 in the chuck.

While I have herein illustrated a work piece a lapping tool 29 whichfloats on its spindle 30,

it must be understood that I may use a rigidly mounted tool and afloating work piece. This can be achieved simply by making the seatslightly over-sized andthe spring I8a. somewhat weak and providing a laprigidly fastened to its spindle. However, in this present embodiment ofthe invention, I have more particularly shown floating laps, and theapparatus of Figures 1 and 2 is adapted to hold the work piece fairlyrigidly so that the method involves, in this present embodiment, arigidly held work piece and a floating lap, it being understood that theapparatus of the invention may be embodied in a lap which is mounted ona fixed axis and a work holder which does not hold the work piecerigidly but allows it to float.

on sheet #2 of the drawings various types of L Referring now to Figure4, an arbor 30 is I shown having a key 3I which may be driven tightlytherein and removed at will. The lap 29 shown in this view has aslightly enlarged central bore 32 to allow free play of the lap on thearbor. The opening 33 transversely of the lap is larger than the ends ofthe key 3| to allow comparatively free play of the lap on the .key,although rotary motion is transferred to the lap by means of the key.This lap and the others -herein described may be made of aluminum,brass, or bronze metals and alloys. Assuming the material to be groundto be a ferrous metal, either cast iron or steel or some other type, asmost work pieces are, the coeflicientof thermal expansion is of theorder of 9 to 13 times 10* at 'moderate temperatures, for example fromthe at its lower end a nut 45 hold the sectionedfreezing point of waterto the boiling point. of water. Brass has a corresponding coeflilcientof about 18. Aluminum has a corresponding coefficient of around 20 andhigher. Bronze has a corresponding coeflicient of about 18 and higher,

depending upon the particular bronze, and an aluminum-copper alloy has acoefficient as high as 27. These metals, aluminum, brass and bronze, arepreferred and give excellent results in actual practice. Each of themwill readily receive abrasive material into its surface. The

abrasive material which is preferably used is diamond "dust, for examplevery fine diamond dust of the order of four hundred mesh grit size Forcertain lapping operations, I may use such abrasives as emery, corundum,fused alumina, or sflicon carbide. The uncharged piece of aluminum,brass, or bronze is placed on a steel plate which has been sprinkledwith the abrasive material and by means of the narrow edge of anothersteel plate (both beingrectangular parallelopipeds), the lap is rolledinto the abrasive dust upon the plate and this serves to charge it withabrasive. It should be understood that the materials mentioned aregiven-byway of example and other materials might be used.

While in the specific embodiment of .the invention described liquid isused to heat the work piece and the lap,-it must be understood thatother apparatus for heating them may,be'employed, such as apparatus fordirectly a blast of ,hot air against the lap and the work piece, or

on the other hand, so far as certain features of the invention areconcerned, the lap alone may be heated and this may be done in anysuitable or convenient manner. I

.,Continuing now with the detailed disclosure of the lapping tools, andreferring again to Figure 4, it will be seen that the key 3| may beremoved and the lap may be changed end for end at will and the keyreinserted. This distribution of possible errors is to this extentachieved. As the lap is free to wobble on the spindle-30, it willreadily adjust itself to the bore of the work piece.

Referring now to Figure 5, an alternative structure for accomplishingthe same purpose is shown'and in this view an arbor 34 has thereon screwthreads 35 which fit loosely in screw threads 36 on the lap. These loosescrew threads allow the lap to have a floating movement on the arbor,thus accomplishing substantially the same result as the constructionshown in Figure 4.

A further means ofaccoinplishing substantially this result for a lapintended to operate on' cylinder and each section having three clutchfaces 42 projecting from each end. These clutch faces and the spacesallowed therebetween allow a loose-connection while imparting rotarymovement between the sections of the lap. The arbor 43 has similarclutch faces at its lower end and a rod 44 is threaded into the arbor 43and has In this 0011- Figure 8 and the circumference of which has agroove 5| therein, around which is a spring wire ring 52. This clutchmember also fits loosely to allow for play laterally between the lap andth arbor. y In Figure 10 a clutch form of connection between arbor andlap is shown which might be used instead of the connection shown inFigure 6. In this view. the clutch portions 54,011 the arbor 56 and theclutch portions 55' on the lap 56 arecircumferentially grooved at 51 andin this groove is placed a spring ring 58.

Because of the reversible feature I uniformity of wear on the lap isproduced and that uniformity promotes uniformity'of lapping in thearticle. By making the lap in two sections,-'eight variations ofarrangement of the lap on its arbor are available. If the lap shown inFigure 9 be considered and the respective ends of the sections belettered as shown, the following arrangements (reading down)arepossible:

OUUH

UJOU BCCD ADDC' DBAA CABB both lap and bore are avoided and the errorswhich creep in due to wear on'the lap are symmetrically distributed.

This result is also furthered by the use. of a lap slightly shorter thana blind bore, in which, after the lap is completely inserted in thebore, it is ,reciprocated a. few times near the blind end of the boreand withoutabrading the entrance and exit portion at the same time.However, for articles with a bore open at both ends, good results may beobtained with a lap longer than the bore as shown in Figure 6. In allembodiments of the invention, it is preferable both to reciprocate androtate the lap relatively to the object being lapped. I i

It will now be understood that in the use of the invention, with eachvertical movement of the lap into the bore and the withdrawaltherestage, the order of lapping of the work piecesfrom only a verysmall amount of metal is removed and the invention contemplates lappingeach of the articles a number of times in any predetermined'sequencethis small amount. If the sequence were always the same, due to theinfinitesimal wear on the lap, the articles finally lap-pad would belapped less than those initially lapped and, therefore, this sequenceshould be varied. If, for example, the temperature is to be raised inten stages, with each work piece lapped a certain amount at eachtemperature shouicflpreferably be different for eachof the ten differentstages and the order of lapping should.

be such that each work piece will be lapped the same number of timesearly in-each stage, the

same number of times late in each stage, and the same number of timesnear the middle of each stage. Various numerical arrangements for theorder of lapping may be devised and for examples of such numericalvariations of lapping, reference may be made to my prior Patents No.1,491,101 and No. 1,486,342. By this process of lapping in a variedsequence, the errors which would creep in due to the wear on the lap maybe made infinitesimally small and by varying 'the change of temperaturebetween any sequences, a larger or less amount of abrading mayice-accomplished by the corresponding movements of the lap. Likewise byVarying the positions of the lap on its arbor, further errors that creepin due to lap wear are eliminated and thus a multiplicity of uniformbores is produced which have the precise size originally desired.

It should be understood that so far as certain features of the inventionare concerned, I may utilize the special lapping rod shown'in Figure 10of my Patent No. 1,486,338, or other similar mechanically expanded laps.

So far as certain features of the invention are concerned, the methodmay be operated in reverse. For example, the kerosene or other liquidmay first be heated to a temperature of around one hundred thirtydegrees Fahrenheit with the articles I immersed therein. A lapping toolaccording to any one of the drawings on Sheet #2 hereof, or any othersuitable form, may be provided which has a very low coeflicient ofthermal expansion and which is of a size substantially to fit the boreof the unlapped article I after it has been expanded by heat. Then theliquid is gradually cooled and the lapping carried out in stages ashereinbefore specified. The result will be a gradual contraction of thearticle against the lap which will remove metal. As a good example of amaterial for the lapping tool according to this embodiment of theinvention, I may use Invar", which is nickel steel containing thirty percent of nickel. At atemperature of twenty degrees centigrade this has acalculated coeflicient of thermal expansion of .9 times 10--'*. TheInvar tool is charged with diamond dust or other abrasive exactly aspreviously specified hereinbefore. This "Invar tool charged withabrasive may have a diameter substantially that of the desired finishedsize of the bore of the article at seventy degrees Fahrenheit. By thismanner of proceeding, the article is brought to finished size when theliquid is cool and the article may be immediately measured to find outif the lapping operation was successfully completed.

It should be understood that so far as certain features of the inventionare concerned, the apparatus may be embodied in instrumentalities forlapping a single article to completion without reference to any others.

In cases where a liquid is used, I prefer to use a liquid which is agood lubricant. Although under certain conditions water might be used, Iprefer hydrocarbon liquids such as light spindle oil 1 or fuel oil, andthe liquid whichis best suited of all so far as I am now aware iskerosene. I select a kerosene which has a high flash point. For example,I have found a kerosene which has a flash point of approximately onehundred thirtyeight degrees Fahrenheit. My upper limit of temperatureunder such conditions is one hundred forty degrees Fahrenheit as it isperfectly feasible to go slightly above the flash point although careshould be taken to keep open flames away from the kerosene. Any of theseliquids can be used at room temperatures at around seventy degreesFahrenheit or, if desired, can be refrigerated almost to their freezingpoints.

It will thus be seen that there has been provided by this invention anapparatus in which the various objects hereina-bove set forth togetherwith many thoroughly practical advantages are successfully achieved. Asmany possible embodiments may be made of the above invention and as manychanges might be made in the embodiaccompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

I claim- A 1. A lapping apparatus comprising a support for an articlehaving an. inner cylindrical surface to be lapped, a container for thesupport and article having a fluid therein, a lap of different ratio ofsize change with like temperature change than the article to be lappedand substantially the size of the cylindrical surface of the article,and means to vary the temperature of the fluid, thereby to change thetemperature of the article to obtain the desired lapping pressure of thelap on the cylindrical surface of the article.

'2. A lapping apparatus comprising a support for an article having aninner cylindrical surface to be lapped, a container for the support andarticle having a fluid therein, a lap of different ratio of size changewith like temperature change 'than the article to be lapped andsubstantially the size of the cylindrical surface of the article, andthermostatically controlled means to vary the temperature of the fluid apredetermined amount to change the temperature of the artiment, aboveset forth, it is to be understood that- I all matter hereirrbefore setforth or shown in the cle to obtain the desired lapping pressure of thethe articles to be lapped and substantially the size of the cylindricalsurfaces of the articles, said lap and each article being adapted to bebrought into lapping position, and means to vary the temperature of thefluid, thereby to change the temperature of the articles to obtain thedesired lapping pressure of the lap on the cylindrical surfaces of thearticles.

4. Apparatus for lapping cylindrical bores, means to hold a plurality ofwork pieces having bores therein comprising a. container, 2. tabletherein adapted to receive said work pieces, a clamp adapted to beplaced upon each work piece to securely hold the same, a lapping tooladapted to fit closely into said bores, said tool and suc-

